Heat grill to medium-high. Lay a sheet of aluminum foil on the grates; place potatoes in a single layer on the aluminum foil. Allow to cook, covered, for about 30 minutes or until tender, turning every once in awhile. Transfer to the part of the grill where there is no foil and cook just until the potatoes have grill marks and the outsides are extra crispy, about 1 to 2 minutes per side.

While the potatoes cook, go ahead and whisk the oil, rosemary, garlic, and salt together. Once the potatoes have been cooked, toss with the garlic-herb oil. Serve immediately.